Signal transmission system



Nov. 2, 1937. J. c. GABRIEL ET AL 7 SIGNAL TRANSMISSION SYSTEM FiledSept .J.C. GABRIEL /NV;//7'ORS. G. ROOM/V 'qq eqe e" Walla 14mg ATTORNEYPatented Nov. 2, 1937 UNITED STATES PATENT OFFICE SIGNAL TRANSMISSIONSYSTEM Application September 8 Claims.

This invention relates to signal transmission systems and moreparticularly to tuning devices for such systems adapted for use atultra-high frequencies.

One object of this invention is to facilitate the tuning of a highfrequency transmission system.

Another object of this invention is to simplify the structure and toincrease the stability of operation of tuning devices for transmissionsystems.

In one illustrative embodiment of this invention, a tuning devicecomprises a metallic tubular member having a substantiallysemi-cylindrical plate at one end thereof. Disposed within the tubularmember is a metallic rod, which preferably is coaxial with the tubularmember and is rotatable about its longitudinal axis. The rod hasslidably mounted thereon a short-circuiting member or plug whichcontacts with the rod and the tubular member and forms an electricalconnection therewith. One or more plate members are mounted on the rodand are disposed adjacent and parallel to the semi-cylindrical plate atone end of the tubular member and form a o condenser therewith.

The rod constitutes an inductive element, the active length, and hencethe inductance, of which may be varied by sliding the short-circuitingmember or plug along the rod. The plate and plate members constitute acondenser in shunt with the inductive element, the capacitance of thecondenser being variable by rotation of the rod and hence of the platemembers carried thereby. Although some distributed capacitance may existbetween the metallic rod and the tubular member, because of therelatively short length of the rod and member, this capacitance issubstantially negligible in comparison with the capacitance of thecondenser formed by the plate and the plate members. The tuning devicein accordance with this invention thus is similar to a resonant circuitof lumped constants.

In a modification of the embodiment described above, the tubular membermay be en compassed by another tubular member, the two members beingspaced by a dielectric material such, for example, as a sheet of mica,and forming a fixed condenser which may be used, for example, as aby-pass condenser to ground.

The invention and the features thereof will be understood more clearlyand fully from the following detailed description with reference to theaccompanying drawing in which:

Fig, l is a perspective view of a tuning device 5, 1935, Serial No.39,280

constructed in accordance with this invention, a portion of the tubularmember being broken away to show details of structure more clearly;

Fig. 2 is a perspective view of a modification of the tuning deviceillustrated in Fig. 1, portions of the outer tubular member being brokenaway, and

Fig. 3 illustrates one typical application of tuning devices constructedin accordance with this invention, as an interstage coupling unit, thetuning device being shown partly in cross-section.

Referring now to the drawing, the tuning de- Vice shown in Fig. 1comprises an elongated tubular or cylindrical member ID having anapertured closure member H at one end and a substantially semi-circularplate l2 at the other end. The tubular member is of a metal having goodelectrical conductivity, such, for example, as copper or aluminum.Disposed within the tubular member ID and coaxial therewith is a rod l3,which also may be of aluminum or copper. A cylindrical metallic memberor plug I4 is slidably mounted on the rod I3 and slidably engages theinner wall of the cylindrical or tubular member ID. A set screw l5 maybe provided for fixing the plug M in a particular position on the rodl3. Another rod 16, preferably of insulating material, is coupled to therod l3 by a sleeve connector I1 and carries a knob l8 for facilitatingrotation of the rods I3 and I5.

The rod 13 carries a pair of semi-cylindrical metallic plate members l9which are disposed on opposite sides of the plate [2 and form acondenser therewith. An electrical connection to the rod l3 may beestablished through a metallic strip 20, preferably of copper, which isprovided with a slot 2| having arcuate surfaces engaging a reducedextension 22 on the rod l3 and is provided also with an integral tab orlug 23 to which a conductor may be secured as by soldering. The strip 20is supported from an insulating bushing 24 carried by a bracket 25mounted on the tubular member ID, the bushing 24 having threaded tapsfor receiving screws 26.

In another embodiment of this invention illustrated in Fig. 2, thecylindrical or tubular member I0 is encompassed by a similar member 21,the two cylindrical or tubular members It! and 21 being spaced by adielectric material, as for example, by a sleeve 28 of mica.

As shown in Fig. 3, tuning devices constructed in accordance with thisinvention may be used as an interstage coupling unit, each stagecomprising an electron discharge device 29 including, for example, aheater type cathode 30, a

control'grid 3|, an anode '32, and a screen grid 33. Suitable batteriesare provided as shown for applying the requisite potentials to thevarious electrodes. The tubular member H1 is connected to the cathodes3G and the strip 26 is connected by a conductor 35 to the conductorconnecting the anode 32 of one'electron discharge device 29 to the grid3| of the electron discharge device in the next stage. The outercylindrical or tubular member 2? may be connected to ground as shown.

It will be clear from Fig. 3. that'the rod I 3 constitutes an inductanceand that the plate l2 and plate members l9 form a condenser in shuntwith the inductance. The cylindrical or tubular members I U and 21,together with the mica sleeve 28, form a by-pass condenser. The in-'ductance of the rod 53 may be varied by sliding the plug member 14 alongthe rod to 'vary the efiective length thereof. The capacitance of thecondenser formed by the plate I2 and plate members l9 may be varied byrotating the rod 13. In the operation of the tuning device, the plug I4may be fixed upon the rod IS in a predetermined position, for'example,approximately one-eighth Wave length of the frequency it is desired totransmit, and the device .may then;

' be'tuned to this frequency by rotating the rod J3.

It will be apparent that this invention provides a simple and compacttuning device which is. structurally rigid and, therefore, insuresstable operation.

Furthermore, it maybe noted that the cylindrical o-r tubular membersHand 21 provide substantially complete shielding of. the

inductance element I3 so that faithful transmission between stages isassured.

Although specific embodiments of the invenf tion have been shown' anddescribed, it will be understood, of course, that modifications may bemade therein without departing from the scope and spirit of thisinvention as defined in theappended claims. 1

' a What is claimed is:

1. 'A'tuning device comprising a pair of conductors disposed one withinthe other, the inner of said members constituting an inductance element,a metallic member ,slidably mounted on the inner of said conductors,said metallic member contacting with and electrically connecting saidconductors, and plate members carried by and electrically connected tosaid conductors and forming a condenser.

' 2. A tuning device comprising a pair of conductors disposed onewithinthe otherand' one of which constitutes the inductive element of thedevice, means for varying the effective length of said one conductor,and means including members'integral 'with' said conductors forming avariable condenser in shunt with said inductive element.

3. A tuning device comprising a tubular metallic member having alaterally extending plate portion, a metallic rod within said tubularmemher and constituting an inductive element, a metallic member slidablymounted onsaid rod and electrically connecting said rod to said tubularmember, and a rotatable plate member mounted on and electricallyconnected to said rod, said plate member beingdisposed in juxtaeposition to said plate portion and forming a condenser therewith.

. 4. A tuning device comprising a pair of coaxial ment, means on saidconductors forming a condenser, and means adjacent one of said con-'ductors and forming another condenser therewith, said means beinginsulated conductors. V W

6. A tuning device comprising a pair of-coaxial conductors the inner ofwhich constitutes an inductance, means for varying the efiectivelengthof said inner conductor, means on said conductors forming avariable condenser, and

another conductor forming another condenser withthe outer of saidcoaxial conductors.

Q 7. A tuning device comprising a pair of icoaxial conductors the innerof which'is rotatable and constitutes an inductance, means for varyingthe efiective length of said inner conductor,

a plate on the outer of said'conductors, a plate i member carried bysaid inner concluctorand ro-' tatable therewith, said plate and platemember being in juxtaposition and forming, a condenser, and a tubularconductor encompassing the outer and forming a conof said coaxialconductors denser therewith.

8. A tuning device comprising a' tubular nietallic member, a rod withinsaid member, said rod constituting an inductive element, adjustablemeans electrically connecting said. rod and from both said said memberfor varying the eifective length'of.

said rod, means carried by said rod and cooperating with'a portion ofsaid member to form a variable condenser in shunt with'said inductiveelement, and another tubular metallic member encompassing said firsttubular member and forming a condenser therewith. 7

.JOHN C. GABRIEL.

GEORGE RODWIN DISCLAIMER 2,097,519.J0hn 0. Gabriel, New York, and GeorgeRoalwin, Randall Manor, N. Y.

SIGNAL TRANSMISSION SYSTEM. Patent dated November 2, 1937. Disclaimerfiled March 24, 1939, by the assignee, Bell Telephone Laboratories,Incorporated.

Hereby enters this disclaimer to claim 1 of said Letters Patent.

Hereby disclaims from the scope of claim 2 of said Letters Patent anytuning device as therein defined except such device wherein the meansforming a variable condenser in shunt with the inductive elementconsists of members integral with the conductors disposed one within theother.

[Ofiicial Gazette April 18, 1989.]

DISCLAIMER 2,097,519.Joh'n, 0. Gabriel, New York, and George Rod'win,Randall Manor, N. Y.

SIGNAL TRANSMISSION SYSTEM. Patent dated November 2, 1937. Disclaimerfiled March 24, 1939, by the assignee, Bell Telephone Laboratories,

Incorporated. Hereby enters this disclaimer to claim 1 of said LettersPatent.

Hereby disclaims from the scope of claim 2 of said Letters Patent anytuning device as therein defined except such device wherein the meansforming a variable condenser in shunt with the inductive elementconsists of members integral with the conductors disposed one within theother.

[Oficz'al Gazette April 18, 1939.]

